JP3237022B2 - Projection exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for manufacturing a high-density integrated circuit such as a semiconductor device and a liquid crystal display device, and more particularly, to a stage device on which a substrate is mounted for correcting the influence of yawing for positioning. The present invention relates to an exposure apparatus including the apparatus.

[0002]

2. Description of the Related Art A schematic configuration of a conventional exposure apparatus of this type is shown in FIG. 3, and an alignment optical system for aligning a substrate in the exposure apparatus and a position of a stage apparatus on which the substrate is mounted and moved. FIG. 4 shows the arrangement of the light beam interferometer and the length measuring beam for measuring the distance. In FIG. 3, illumination light from an illumination optical system (not shown) transmits through a reticle R and is condensed on a substrate P via a projection optical system PL. The substrate P is placed on a stage S that can move in a two-dimensional direction, and moves two-dimensionally in a plane. An X-direction moving mirror MRx and a Y-direction moving mirror MRy are provided on the stage S along the moving direction, and are perpendicular to the light wave interferometers (stage interferometers) Lx and Ly as shown in FIG. And the optical axis A of the projection optical system PL
The position of the stage S is detected by reflecting the laser beams Bx and By emitted in the direction passing through the stage. One of the movable mirrors, for example, the movable mirror MRy is further irradiated with two laser beams Bθ1 and Bθ2 in parallel with the optical axis of the laser beam By, and the difference between the respective measurement distances of the laser beams Bθ1 and Bθ2 is obtained. The rotation deviation (yaw) from the reference position of the stage S is detected based on this. As shown in FIG. 4, alignment marks Mx, My1, and My2 are provided on the substrate P, and the alignment marks Mx, My1, and My2 are respectively detected by the alignment optical systems Ax, Ay1, and Ay2 to position the substrate P with respect to the apparatus.

When the positions of the alignment marks My1 and My2 of the photosensitive substrate P in the Y direction are determined using the alignment optical systems Ay1 and Ay2 in order to position the substrate with respect to the apparatus, the positions are determined on the basis of predetermined design values. To move the stage S to dispose the alignment mark near the detection area of the alignment optical system. Stage S from there
Is moved in the Y direction at a constant speed and in a certain range (scan)
Then, the diffracted light or reflected light from the alignment mark during scanning is detected as an alignment signal by the alignment optical systems Ay1 and Ay2. At this time, signals obtained by the alignment optical systems Ay1 and Ay2 are stored in synchronization with the position of the stage measured by the stage interferometer Ly (laser light By), and diffracted light or reflected light from the alignment mark is detected. Stage interferometer L
The output (absolute coordinates) of y has been determined as the position of the marks My1 and My2 in the Y direction.

On the other hand, when determining the position of the alignment mark Mx in the X direction, the stage interferometer Lx (laser beam B
If the stage S is scanned in the X direction while detecting the position in x), and the alignment signal from the mark is detected by the alignment optical system Ax, it can be obtained in the same manner as described above. By the way, generally, the alignment optical systems Ax, Ay1, Ay2 are arranged eccentrically with respect to the optical axis A of the projection optical system PL. Therefore, the laser beams Bx and By of each stage interferometer do not pass through the detection center of the alignment optical system. Therefore, when the position measured by each stage interferometer when the alignment mark is detected by the alignment optical system is used as the mark position, this position must include a so-called Abbe error with respect to the actual alignment mark position. become. In other words, if the stage has a rotational displacement from a position that should originally exist according to the position, an error occurs in the detection result of the alignment mark position. Therefore, conventionally, at the start and end of stage scanning,
Alternatively, the yawing of the stage is measured at regular intervals during scanning using a yawing interferometer (laser beams Bθ1, Bθ2), and the average value is obtained. The average value is used as a yawing amount (correction value) to be corrected, and the yaw amount is corrected by adding the average value to the stage position obtained as the alignment mark position.

[0005]

However, in the prior art as described above, since only the average yawing amount during the movement of the stage is obtained, the case where the yawing amount changes successively according to the position of the stage is obtained. Has a problem that an accurate correction value cannot be obtained, and therefore, an alignment mark position cannot be obtained accurately.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a projection exposure apparatus capable of accurately correcting a yawing amount that changes successively during movement of a stage so as to accurately detect an alignment mark position. The purpose is to provide.

[0007]

In order to solve the above-mentioned problems, the present invention provides a stage (S) on which a substrate (P) is placed and two-dimensionally moves in a plane; A laser interferometer (Lx) that irradiates a movable mirror (MRx, MRy) disposed on the stage with a laser beam (Bx, By) almost vertically and detects a two-dimensional position of the stage (S). , Ly) and two laser beams (Bθ1, Bθ2) having an optical axis parallel to the optical axis (Bx, By) of the laser beam of the lightwave interferometer are irradiated to the movable mirror (MRx, MRy). Rotation amount detecting means (θ1, θ2) for detecting the rotation amount of the stage (S) based on the difference in the measurement distance between the two laser beams (Bθ1, Bθ2); and a reference pattern formed on the substrate. Reference pattern detection means for detecting (Mx, My1, My2) Ax, Ay1, Ay2)
And position correction means for correcting the two-dimensional position based on the amount of rotation while setting the two-dimensional position when the reference pattern is detected by the reference pattern detection means as the position of the reference pattern. In a projection exposure apparatus for positioning a substrate based on the two-dimensional position and projecting and exposing a pattern formed on a mask onto the substrate via a projection optical system (PL), a light wave interferometer (Lx, Ly) )
Means for sequentially detecting the amount of movement of the stage during the movement of the stage from an arbitrary position in the plane as the first pulse (P1, P2);
1, θ2) includes means for detecting, as the second pulse (P3), the amount of rotation that sequentially changes with respect to an arbitrary position during the movement of the stage; light wave interference during the movement of the stage from the arbitrary position A pulse correcting means (2) for correcting the first pulse by adding the second pulse (P3) by the rotation amount detecting means to the first pulse (P1, P2) sequentially detected by the length measuring device. I decided that.

[0008]

In the present invention, an up / down pulse corresponding to the yawing amount obtained by the yawing interferometer is constantly added to the up / down pulse of the length measuring device for measuring the position of the stage. , Can be corrected in real time even if changes successively.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic configuration of the present invention is exactly the same as that of the conventional apparatus, but the amount of movement of the stage detected by the light wave interferometer and the amount of change in yawing detected by the yawing interferometer are detected by pulses. However, the difference is that a circuit for adding each pulse is provided. FIG. 2 is a diagram showing an arrangement of an alignment optical system and a measuring beam of a light wave interferometer (stage interferometer) in a projection exposure apparatus according to an embodiment of the present invention. In the figure, the interval between two beams of the yawing interferometer is configured to be the same as the amount of deviation of the alignment optical system from the beam of the stage interferometer. That is, the deviation amounts of the respective alignment optical systems Ay1 and Ay2 from the laser light By are represented by a1 and a2, respectively, and the deviation amount of the alignment optical system Ax from the laser light Bx is represented by a3. A1 = a for the total beam interval a
They are arranged so that 2 = a3 = a. Also, the resolution of the stage interferometer and the yaw interferometer are the same (for example,
0.02 μm).

FIG. 1 is a block diagram showing processing of a signal (up-down pulse) obtained by a stage interferometer and a yawing interferometer of a projection exposure apparatus according to an embodiment of the present invention. Up-down pulse P when stage S moves
1 and P2 are measured by the stage interferometer Lx and the stage interferometer Ly, respectively, and an up pulse and a down pulse are separately output, and the displacement of the coordinates of the interferometer in the + and-directions corresponding to the moving amount of the stage. Is shown. At the time of measuring the alignment mark position, the stage S in FIG. 3 is scanned at a constant speed to generate a pulse in each interferometer according to the movement of the stage position. By inputting to the counter, the input address of the alignment signal having a unit of 0.02 μm is determined. The up / down pulse P3 is measured by the yawing interferometers θ1 and θ2 and output similarly, and indicates a displacement corresponding to a change in the yawing amount of the stage. When measuring the position (coordinate position) of the alignment mark in the X direction using the alignment optical system Ax, the up / down pulse P1 is selected by the selection circuit 1 and output to the pulse addition circuit 2.

If yawing occurs during scanning, an up-down pulse P3 is measured as a yawing amount by the yawing interferometers θ1 and θ2. As described above, the resolution of the stage interferometer and that of the yaw interferometer are the same, and the displacement a3 is the same as the beam interval a of the yaw interferometer. Equivalent to that of P1. Therefore, the pulse P
Reference numeral 3 denotes a correction amount of a detection error of the alignment optical system Ax due to yawing.

However, the directions indicated by the up pulse and the down pulse of the pulse P3 obtained by the yawing interferometer (the rotation direction of the stage) and the directions indicated by the respective pulses of the stage interferometer (the traveling direction of the stage) are the same. Not limited (polarities of interferometers are different). Therefore, the pulse adding circuit 2 adds the pulse P3 to the pulse P1 after selecting whether or not to exchange the up pulse and the down pulse in the replacing circuit 3 and appropriately replacing the pulse. The up-pulse Pu and the down-pulse Pd thus obtained are approximated to an up-down pulse indicating the position of a mark (without Abbe error) obtained by irradiating the detection center of the alignment optical system Ax with the X-direction interferometer beam Bx. Is done. By determining the input address of the alignment signal using the pulses Pu and Pd, it is possible to correct the yawing that changes successively during scanning in real time, and to accurately determine the position of the alignment mark.

On the other hand, alignment optical systems Ay1, Ay2
When the positions (coordinate positions) of the alignment marks My1 and My2 in the Y direction are measured using the same, the up / down pulse P2 is selected by the selection circuit 1 in the same manner as described above, and the up / down pulse P3 is generated by the pulse addition circuit 2. What is necessary is just to add. In the above embodiment, the interval between the two beams of the yawing interferometer and the amount of deviation of the alignment optical system from the beam of the stage interferometer are the same. For example, the ratio may be 1: 2. At this time, by dividing the up / down pulse P3 by the frequency dividing circuit 4, the yaw correction amount when measuring the alignment mark position is formed as a pulse P4 converted into a displacement amount represented by one pulse of the pulse P1. be able to. In addition, the resolution of the yaw interferometer and that of the stage interferometer are made different so that
In the case where μm and 0.02 μm are set and the ratio between the beam interval and the amount of deviation of the alignment optical system is set to 1: 1, the frequency of the up / down pulse P3 may be divided. That is, the stage interferometer L
An up / down pulse is generated according to the ratio of the resolution of x and Ly to the resolution of the yawing interferometers θ1 and θ2, and the ratio of the beam interval of the yawing interferometers θ1 and θ2 to the deviation amount of each alignment optical system Ax, Ay1, Ay2. The frequency division and division may be performed as appropriate.

[0014]

According to the present invention, even if errors in the rotation direction change successively during the movement of the stage, they are corrected in real time, so that the position of the alignment mark can always be detected accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing processing of signals obtained by a lightwave interferometer and a yawing interferometer in a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of an alignment optical system and a measuring beam of a lightwave interference measuring device in a projection exposure apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a projection exposure apparatus according to a conventional technique.

FIG. 4 is a diagram showing an arrangement of an alignment optical system and a measuring beam of a lightwave interference measuring device in a projection exposure apparatus according to a conventional technique.

[Explanation of symbols]

 2 pulse addition circuit 4 frequency division circuit Lx, Ly Laser interferometer θ1, θ2 Yawing interferometer Ax, Ay1, Ay2 Alignment optical system

Claims (1)

(57) [Claims] A stage on which a substrate is placed and which moves two-dimensionally in a plane; and a laser beam is irradiated substantially perpendicularly to a movable mirror arranged on the stage along a moving direction of the stage. An optical interferometer for detecting a two-dimensional position of the stage; and irradiating the movable mirror with two laser beams having an optical axis parallel to the optical axis of the laser beam of the optical interferometer. Rotation amount detection means for detecting the rotation amount of the stage based on a difference in the measurement distance between each of the two laser beams; reference pattern detection means for detecting a reference pattern formed on the substrate; Position correction means for setting the two-dimensional position when the reference pattern is detected by the reference pattern detection means as the position of the reference pattern, and correcting the two-dimensional position based on the rotation amount. , The correction In a projection exposure apparatus that positions the substrate based on the obtained two-dimensional position and projects and exposes a pattern formed on a mask onto the substrate via a projection optical system, the lightwave interference measuring device includes: Including means for sequentially detecting a movement amount of the stage as a first pulse during movement of the stage from an arbitrary position in the plane,
The rotation amount detection means includes means for detecting the rotation amount sequentially changing with respect to the arbitrary position during the movement of the stage as a second pulse; during the movement of the stage from the arbitrary position, Adding the second pulse by the rotation amount detecting means to the first pulse sequentially detected by the light wave interferometer;
A projection exposure apparatus comprising pulse correction means for correcting the above pulse.